FIG. 22 and FIG. 23 show a conventional type of terminal cover disclosed in Japanese Patent Laid-Open Publication No. SHO 59-114897. In the figures, designated at the reference numeral 10 is a frame for electrical equipment such as an electro-magnetic contactor, at 12 a terminal plate of each pole projecting to the outside of the frame 10, at 13 a terminal screw attached to each of the terminal plates 12, at 14 two pieces of interpole insulating barrier plate partitioning the terminal plate 12 of each pole, and at 16 a terminal cover respectively.
The terminal cover 16 has two pieces of vertical polar body 22 and a U-shaped elastic engaging piece 24 each provided downward on the rear face thereof (toward the side of the electrical equipment). The elastic engaging piece 24 is integrally connected to the terminal cover 16 at one edge of the piece with the other edge thereof which is a free edge 24a to be open, and a counter claw section 26 is provided on the outside of the piece adjacent to the free edge 24a. Formed on the terminal cover 16 is an opening 28 for inserting a tool T for removal from the upper side of the cover toward the free edge 24a of the elastic engaging piece 24.
The terminal cover 16 is mounted onto electrical equipment in the following way; namely, in a state where the terminal cover 16 is set to the upper side of a top surface 10a of the frame 10 for the electrical equipment in the direction indicated by the arrow A in FIG. 22, guide grooves 20 are provided in the interpole insulating barrier plates 14 in the vertical direction to the terminal plate 12 respectively, and the vertical polar bodies 22 which hang down are inserted to the guide grooves 20 each vertically formed on the side face of the interpole insulating barrier plate 14 for engagement respectively, and the terminal cover 16 is pressed down in a state where the sticks are inserted and engaged therein. When the terminal cover 16 is pressed down as far as a position where the cover contacts the top surface 10a of the frame 10, the counter claw section 26 provided adjacent to the free edge 24a of the elastic engaging piece 24 is engaged in a recess 30 for engagement formed on the side face 10b of the frame 10. With this operation, the terminal cover 16 is fixed to the frame 10 in a state where the top surface 10a of the frame 10 is covered by the terminal cover 16.
When the terminal cover 16 is removed from the frame, the tool T for removal is inserted from the opening 28 into a section between the free edge 24a of the elastic engaging piece 24 and the side face 10b of the frame 10, the counter claw section 26 is removed out of the recess 30 for engagement by elastically deforming the free edge 24a in the direction indicated by the arrow B in FIG. 23, and the terminal cover 16 is removed from the frame 10 by being held upward in a state where an engagement relation between the counter claw sections 26 and the recess 30 for engagement is released.
In the conventional type of terminal cover, the engagement between the counter claw section 26 and the recess 30 for engagement is obtained, in a state where the terminal cover is mounted on the frame, just by pressing down the counter claw section 26 to the recess 30 for engagement, and for this reason, if some counter force is applied to the engagement realized by pressing the counter claw section 26 to the recess 30 for engagement from one direction under such bad environments that vibrations or shocks are applied onto the electrical equipment, the engagement therebetween may not be maintained because the counter claw section 26 may be disengaged from the recess 30 for engagement thereby or the engagement between the counter claw section 26 and the recess 30 for engagement may become unstable due to deformation of the counter claw section 26 within the recess 30 for engagement for each application of the force to the engagement in the reverse direction and abrasion or disappearance of contact surfaces between the counter claw section 26 and recess 30 for engagement, so that a mounted state of the terminal cover on the frame is not reliable and durable.
Also, in the conventional type of terminal cover, when the electrical equipment is an electromagnetic contactor or the like, there is sometimes a case where the recess 30 for engagement is provided on the wall surface of a frame for the electro-magnetic contactor and an adjacent portion of this wall surface may face to a wall surface of an arc box for cutting off a current. As inside of the wall surface of the arc box is adjacent to a portion where a high-temperature arc under high pressure is generated, the portion of the recess 30 for engagement has a high temperature during the operation of the electromagnetic contactor, and under such bad environmental conditions, the counter claw section 26 engaged in the recess 30 for engagement is also put under the high temperature. For this reason, heat loss such as heat deformation or melting occurs in the counter claw section 26, which causes the counter claw section 26 to be disengaged from the recess 30 for engagement or to be stuck or adhered thereto, so that it may be impossible to remove the terminal cover 16 from the electrical equipment.